VFD Conversion Questions

[TorontoBuilder]

Do you think a motor like this would need a stepped pulley setup? I'm really trying to avoid that as I always find them clunky, I can work it in if needed though.

I'm the meantime I'll install a smaller pulley to make it 1:1 instead of a 2:1 and see what that does. I don't know for sure what I want out of the machine yet, I've never owned a mill before, but I don't want to paint myself into a corner either. I'd like to do whatever I'm capable of to keep the machine operating in its limits.

Again I'm completely green when it comes to 3 phase motors, I appreciate the feedback. I find fabrication fun but calculating numbers for motors isn't my forte.

I have a South Bend 9A that I've used for several years, I'm reasonably confident with it. I was originally on the market for a smaller machine but this one popped up for cheap and I thought it'd be a fun project. This setup will be good enough for me to learn on, once I need more power I'll source a better suited motor and VFD setup. This motor and VFD combo cost me $100, so I'm not super concerned about replacing it in the future.

Given the motor you have you wont get much use out of the VFD because you can't likely operate outside of a band of about 40-70 hz without having issues.

That means yeah you should have a stepped pulley system. Maybe with only two pulley sizes but likely better with 3, unless you were to change both the motor and VFD and then I'd still use stepped pulley with two steps.

 

[Ischgl99]

I have a multistep pulley on my Burke Millrite and run a VFD on a 1 hp motor. My motor is 900 rpm, so ignore the pulley step sizes, they will be different for your motor. I usually only change the belt when changing between steel and aluminum, and very small cutters and larger end mills or face mills and probably only use the lowest, highest and middle groove for 95% of what I do. For a hobbyist, you can get away with not running at optimum speeds, so I wouldn’t let a step pulley be a deterrent with the right kind of adjustment setup.

For the Burke, the motor has two bolts holding it to the drive frame, one round bolt hole to swivel and one slotted to swing the motor. Simply loosen those bolts, swing the motor towards the spindle pulley, change the belt setting and swing back and retighten the bolts. Very quick to do. If you could build something like that for your mill, you can change speeds very quickly. Or, the idler pulley you have now might work too if you could come up with a taller pulley that covers the different groove heights.

 

[NikolaiBorjeski]

Given the motor you have you wont get much use out of the VFD because you can't likely operate outside of a band of about 40-70 hz without having issues.

That means yeah you should have a stepped pulley system. Maybe with only two pulley sizes but likely better with 3, unless you were to change both the motor and VFD and then I'd still use stepped pulley with two steps.

I'll likely end up getting a better setup for the mill and setting this VFD aside for my lathe if I ever find a 1/3 or 1/2hp motor for it. Is there a specific model of motor I should be looking for to use as a guideline?

I have a multistep pulley on my Burke Millrite and run a VFD on a 1 hp motor. My motor is 900 rpm, so ignore the pulley step sizes, they will be different for your motor. I usually only change the belt when changing between steel and aluminum, and very small cutters and larger end mills or face mills and probably only use the lowest, highest and middle groove for 95% of what I do. For a hobbyist, you can get away with not running at optimum speeds, so I wouldn’t let a step pulley be a deterrent with the right kind of adjustment setup.

For the Burke, the motor has two bolts holding it to the drive frame, one round bolt hole to swivel and one slotted to swing the motor. Simply loosen those bolts, swing the motor towards the spindle pulley, change the belt setting and swing back and retighten the bolts. Very quick to do. If you could build something like that for your mill, you can change speeds very quickly. Or, the idler pulley you have now might work too if you could come up with a taller pulley that covers the different groove heights.

Thinking if I need to use a stepped pulley setup I'll put my idler on a floating axle so it can move up and down depending on where the belt is. I'd prefer to have the motor hard mounted just to keep things more simple. This machine looks like it used to have a setup similar to your Burke, but its all long gone.

 

[TorontoBuilder]

I'll likely end up getting a better setup for the mill and setting this VFD aside for my lathe if I ever find a 1/3 or 1/2hp motor for it. Is there a specific model of motor I should be looking for to use as a guideline?


Thinking if I need to use a stepped pulley setup I'll put my idler on a floating axle so it can move up and down depending on where the belt is. I'd prefer to have the motor hard mounted just to keep things more simple. This machine looks like it used to have a setup similar to your Burke, but its all long gone.

eMotors Direct - Canada's Online Source for Electric Motors, Gearing, and Controls

www.emotorsdirect.ca

Inverter duty motor. 10:1 constant torque turn down ratio, 6hz low end. 2 HP and under $400 brand spanking new with warranty

 

[TorontoBuilder]

eMotors Direct - Canada's Online Source for Electric Motors, Gearing, and Controls

www.emotorsdirect.ca

Inverter duty motor. 10:1 constant torque turn down ratio, 6hz low end. 2 HP and under $400 brand spanking new with warranty

or the 1.5 HP same series

$350

TECO-Westinghouse RF1/54 | Teco Westinghouse RF1/54 - General Purpose - 1 1/2HP 1800RPM 3PH 230V/460V TEFC 145T Frame Rolled Steel Rigid Weight: 40 lbs | eMotors Direct | Canada

Teco Westinghouse RF1/54 - General Purpose - 1 1/2HP 1800RPM 3PH 230V/460V TEFC 145T Frame Rolled Steel Rigid Weight: 40 lbs

www.emotorsdirect.ca

 

[NikolaiBorjeski]

or the 1.5 HP same series

$350

TECO-Westinghouse RF1/54 | Teco Westinghouse RF1/54 - General Purpose - 1 1/2HP 1800RPM 3PH 230V/460V TEFC 145T Frame Rolled Steel Rigid Weight: 40 lbs | eMotors Direct | Canada

Teco Westinghouse RF1/54 - General Purpose - 1 1/2HP 1800RPM 3PH 230V/460V TEFC 145T Frame Rolled Steel Rigid Weight: 40 lbs

www.emotorsdirect.ca

Oh wow... That's wayyyy cheaper than I was expecting. I work in the hot tub industry where a single phase pump starts at $600. I was expecting closer to $1000.

Are chinese VFDs worth it or should I hold out for a used name brand one?

 

[NikolaiBorjeski]

If I got one of those 2HP motors and an appropriately sized VFD, do you think I'd be okay running it with a 1:1 pulley setup and avoiding stepped pullies? Or should I still be investigating into a 2 or 3 step pulley?

 

[mksj]

Anyway you look at it you will need at least 2 and possibly 3 step pulley speeds if you want a speed range in the 100-6000 RPM range. Personally I have a full size knee and I never have pushed the top end speed past 4000 RPM. I would go with a minimum of a 2 Hp 1750 RPM motor and if you are going to do any slow speed work consider a 3 Hp. My issue with the cheap generic Chinese VFD's is there manual and programming is very poor and limited, they have a high initial failure rate, and the wiring paths/capacitors often fail due to the quality pf the build. That being said, if the budget is tight then you can give one a try. Vevor, Lapond are probably at the bottom of the heap.

 

[TorontoBuilder]

If I got one of those 2HP motors and an appropriately sized VFD, do you think I'd be okay running it with a 1:1 pulley setup and avoiding stepped pullies? Or should I still be investigating into a 2 or 3 step pulley?

At 1:1 pulley ratio with a 1750 rpm motor where you can go from 6 to 120hz your range of speeds would be ~175 to 3500.

That is well within my usual speed range. Our bridgeport has a 2 HP motor and variable drive head. We have a chinese VFD on the mill and haven't had an issue with it. I have 2 other chinese VFDs that work fine, but our old lathe we added a Teco VFD because we wanted to use braking which the chinese VFDs tend to suck at.

I'm comfortable recommending this 2.2 KW model at 158 bucks from amazon since I have two that have worked well.

https://www.amazon.ca/gp/product/B07T55DW7Z/ref=ppx_yo_dt_b_search_asin_title?ie=UTF8&th=1

 

[TorontoBuilder]

Anyway you look at it you will need at least 2 and possibly 3 step pulley speeds if you want a speed range in the 100-6000 RPM range. Personally I have a full size knee and I never have pushed the top end speed past 4000 RPM. I would go with a minimum of a 2 Hp 1750 RPM motor and if you are going to do any slow speed work consider a 3 Hp. My issue with the cheap generic Chinese VFD's is there manual and programming is very poor and limited, they have a high initial failure rate, and the wiring paths/capacitors often fail due to the quality pf the build. That being said, if the budget is tight then you can give one a try. Vevor, Lapond are probably at the bottom of the heap.

I agree with the 3 step pulley necessity in order to attain the full range of speeds the mill was designed for.
I already mentioned the simplest 1:1 pulley option. This would likely work well enough for many uses, but I can't stress enough the value of the step pulley option.

As has been said many times before in relation to machines and VFDs, with step pulley set-up, you can design the ratios to to provide a full range of speeds with a "normally set" 1:1 mid range pulley in the middle of the cone stack to provide speeds between 180 to 3600 rpm* in order to minimize the need for frequent belt changes. Then two step options for very low and very high for those times you really need to go beyond the adjustability of the VFD.

*with the previously recommended motor

As you can also see the low and the high end speed ranges will still offer fair range in case you need to temporarily switch operations without belt change

Example using 9" / 6" / 3" step pulleys on each end

Low Speed range 60 rpm @ 6 hz - 600 rpm @ 60hz - 1200 rpm @ 120hz

High Speed range 450 rpm @ 6hz - 6000 rpm @ 66.6 hz

Note the high speed ratio requires the user not to exceed 66.6 hertz or it will exceed the spindle speed capacity. As a safety device such a machine should have a separate tachometer installed on the mill to display the actual spindle speed rather than the motor speed the VFD is capable of displaying.

It is simple to install a hall effect sensor when the mill head is wide open If Nikolai is doing that then he should install a machining computer to calculate speeds and feeds as well, since this would be very helpful for new machinist to know the optimal rpm for facing with a huge fly cutter or drilling with a tiny drill in brass and aluminum.

Here is a pic of the tachometer and controller my friend and I developed for our lathes and mills. This is V2 and there will be a V3 that includes tables for materials and tooling so that the user does not need to consult external reference material in order to enter recommended surface feet per minute speeds or tool chip loads.